In an effort to reduce power consumption and extend battery life, many mobile stations will enter an idle or sleep state for significant portions of time when a mobile station is not in an active call, during which at least portions of the receiver circuitry are effectively deactivated and power usage is correspondingly reduced. During this time, the mobile station will periodically wake up thereby enabling paging channel messages to be received, while the portions of the receiver that are necessary for receiving paging signals are activated. Conversely, paging channel messages can not be received during the periods of time in which the portions of the receiver circuitry, that are necessary for receiving paging channel messages, are not activated. Generally, the anticipated activation periods of the mobile station are known to the base station in order that the transmission of the paging channel messages from the base station can be coordinated with the periods of time during which the portion of the mobile station associated with the receiver circuitry is activated, and correspondingly the mobile station is able to receive the messages. The periodic activation of receiver circuitry for the purpose of receiving paging channel messages, when the mobile station is not in an active call, is sometimes called slotted mode.
Because the related power usage is related to the amount of time during which the corresponding portions of the mobile station are activated, there is an incentive to maximize the amount of time that the corresponding portions of the mobile station are deactivated including maximizing the amount of time between activations. However maximizing the amount of time that the corresponding portions of the mobile station are deactivated including the amount of time between activations can have an adverse effect on the availability of the mobile station for receiving paging messages, where delays in the ability to transmit and receive paging messages can increase the amount of time required to set up a call. Where the delay is significant and/or corresponds to a noticeable amount, the delay can negatively affect a user's overall usage experience. More specifically, a paging delay refers to the duration of time between, when the base station receives a request to page a mobile station, and when the page is actually sent. For applications, such as push-to-talk or web browsing applications, any meaningful delays associated with call set up can be especially noticeable.
For some networks, such as a cellular wireless communication networks, which are implemented in accordance with at least some traditional forms of code division multiple access (CDMA) protocols, a slot cycle index of 1 or 2 is normal. A slot cycle index of 1 or 2 can translate into possible paging delays of up to 2.56 seconds for a slot cycle index value of 1, and paging delays of up to 5.12 seconds for a slot cycle index value of 2. Generally, the maximum possible paging delay corresponds to the length of the slot cycle, which is given by the formula 1.28×2 i seconds, where i is the value of the slot cycle index.
In Kelley et al., U.S. Pat. No. 6,822,973, an apparatus and method for operating in reduced slotted mode, which correspondingly reduces the paging delay during the portion of time in which the mobile station and the base station are operating in a reduced slotted mode, is described. In at least some instances, the operation in reduced slotted mode is intended for predetermined periods of time following the release of a traffic channel, where the likelihood of an incoming paging message is thought to be more significant, after which the operation of mobile station and the base station returns to a slotted mode having a slot cycle index value corresponding more closely to normal operation.
During the reduced slotted mode, the slot cycle index can have a negative value, which can reduce the length of the slot cycle to less than 1.28 seconds. For example, a slot cycle index value of −3 results in a slot cycle having a length of 160 ms. Where the maximum paging delay corresponds to the length of the slot cycle, the likelihood of a noticeable paging delay, where the slot cycle index value is negative, is correspondingly reduced. Presumably, during a period of operation corresponding to the reduced slotted mode, the amount of power being consumed within the mobile station receiver is correspondingly increased.
Previous reduced slotted modes are largely associated with slot cycle index values, that have an integer value. The inventors of the present application have recognized that one might be better able to balance the power savings with the potential paging delays associated with a slotted mode of operation, such as reduced slotted mode, if greater granularity in selecting a slot cycle index value was available. Consequently, a method and apparatus for managing paging related delays, which would allow for the use of an effective fractional slot cycle index, as part of a slotted mode of operation including a reduced slot cycle period, would be beneficial.